The aim of this project is to investigate macrophage mediated cytotoxicity in patients with malignancies in order to define how macrophage cytotoxic function is altered in these patients. Recently, it has been shown that human macrophages acquire enhanced cytotoxicity for tumor cells after incubation in mediator-rich supernatants obtained from antigen stimulated lymphocytes (MAF). Macrophages obtained from cancer patients as well as normal macrophages will be activated with MAF or lipopolysaccharide (LPS) and tested from their ability to kill several known sensitive tumor targets. Since it is known that human macrophages won't kill tumor cells unless first activated with MAF or LPS, we would like to examine whether macrophages from cancer patients have increased cytotoxicity for target cells prior to any stimulation. Finally, macrophages obtained from cancer patients will be tested for their capacity to become cytotoxic for autologous target cells. For these experiments, autologous lymphocytes for generating MAF) as well as autologous macrophages and tumor cells will be utilized. If a cancer patient's macrophages can be induced to kill autologous tumor targets, then the ability of serum factors from these patients to influence macrophage tumor interactions will be studied. Any serum factor which either enhances or decreases macrophage cytotoxicity will be isolated and characterized. These purified inhibitory or enhancing factors will then be utilized to make monoclonal antibodies directed against the particular factor. These antibodies might have future significance as a diagnostic tool in the treatment of cancer.